Where does stall collide?

In turbomachinery, rotating stall is a flow instability in an axial compressor in which one or more cells of stalled, low-flow passages form and travel around the compressor annulus, degrading the pressure rise and often preceding the violent system-level oscillation called surge. It is a property of the whole compression system rather than of a single blade. Greitzer's 1976 Surge and rotating stall in axial flow compressors gave the dynamic model that distinguishes the two. The referent is a propagating aerodynamic breakdown inside a machine, and although it shares the word and a root in flow separation with a wing's stall, it is a distinct, system-level construct, and wholly unrelated to a stalled ribosome.[1]

Unit

The onset flow coefficient and the number and speed of stall cells around the annulus

Recovery means

Recovered by raising the mass flow or opening the throttle to restore attached, axisymmetric flow

Measured by

Detected from circumferential pressure or velocity traces showing cells rotating at a fraction of rotor speed

In aerodynamics, stall is the sudden loss of lift that occurs when a wing or airfoil exceeds its critical angle of attack: beyond that angle the airflow separates from the upper surface, lift collapses and drag rises sharply, regardless of how fast the aircraft is moving. A stall is therefore a condition of the flow over the wing, not of the engine. Anderson's Fundamentals of aerodynamics treats stall as the breakdown of attached flow past the maximum lift coefficient. The referent is the separation-driven collapse of lift on a lifting surface, measured against angle of attack, and it is a different construct from a compressor's annular instability or a ribosome halting on a transcript.[2]

Unit

The angle of attack and lift coefficient at which flow separates and lift collapses

Recovery means

Lift is recovered by reducing the angle of attack so the flow reattaches to the wing

Measured by

Identified from the lift-curve peak (maximum lift coefficient) and the critical angle of attack in wind-tunnel or flight data

In molecular biology, ribosome stalling is the arrest of a ribosome partway along a messenger RNA during protein synthesis, caused by damaged or structured mRNA, rare codons, certain nascent-peptide sequences, or a missing stop signal. Persistent stalling is not merely a pause: it triggers rescue and quality-control pathways that split the ribosome and degrade the faulty product. Joazeiro's 2017 review Ribosomal stalling during translation describes how stalled ribosomes become substrates for ribosome-associated quality control. The referent is a halt in translation on a transcript, and it has nothing in common with a wing losing lift or a compressor's annular instability beyond the shared word.[3]

Unit

A translating ribosome arrested at a position along an mRNA

Recovery means

Stalled ribosomes are rescued and recycled by quality-control pathways that split the subunits and degrade the incomplete product

Measured by

Mapped by ribosome profiling and related assays that reveal ribosome density piling up at stall sites